Noise within an open space is problematic for people working within the open space. For example, many office buildings utilize a large open office area in which many employees work in cubicles with low cubicle walls or at workstations without any acoustical barriers. Open space noise, and in particular speech noise, is the top complaint of office workers about their offices. One reason for this is that speech enters readily into the brain's working memory and is therefore highly distracting. Even speech at very low levels can be highly distracting when ambient noise levels are low (as in the case of someone answering a telephone call in a library). Productivity losses due to speech noise have been shown in peer-reviewed laboratory studies to be as high as 41%. Office acoustic design has gotten very good at reducing ambient noise, but the quiet environments that have been created can cause speech noise to contrast strongly with the quiet. Even quiet offices, therefore, can create a level of speech intelligibility that is highly distracting. The intelligibility of speech can be measured using the Speech Transmission Index (STI).
Another major issue with open offices relates to speech privacy. Workers in open offices often feel that their telephone calls or in-person conversations can be overheard. Speech privacy correlates directly to intelligibility. Lack of speech privacy creates measurable increases in stress and dissatisfaction and is one of the top complaints of workers about their office environments.
Open office noise is typically described by workers as unpleasant and uncomfortable. Speech noise, printer noise, telephone ringer noise, and other distracting sounds increase discomfort. All of these can be summarized to three acoustic problems: (1) excessive and distracting levels of speech intelligibility, (2) lack of speech privacy, and (3) lack of acoustical comfort. All three of these problems are becoming increasingly important as office densification accelerates. The higher the utilization of office space, the more acoustical problems come to the fore. This discomfort can be measured using subjective questionnaires as well as objective measures, such as cortisol levels.
In one type of prior art, the issues associated with office noise have been attacked by facilities professionals. Noise absorbing ceiling tiles, carpeting, screens, furniture, and so on, have become the standard and office noise has been substantially decreased. Reducing the noise levels does not, however, directly solve the three problems outlined above, as they relate to the intelligibility of speech. Speech intelligibility can be unaffected, or even increased, by the noise reduction measures of facilities professionals. Another type of prior art is injecting a pink noise or filtered pink noise (herein referred to simply as “pink noise”) into the open office. Pink noise is effective in reducing speech intelligibility, increasing speech privacy, and increasing acoustical comfort. However, listeners complain that pink noise sounds like an airplane environment, or complain that the constant air conditioning like sound of the pink noise becomes fatiguing over time.
As a result, improved methods and apparatuses for addressing open space noise are needed.